A reader might draw from the passage that the man with the umbrella is extremely persistent because of many reasons. One of many reason is about how the man with the umbrella chased the author, even when he ran away (stated in paragraph 4): "Convinced that I was dealing with a madman, I tried to escape. But the man followed me, wordlessly continuing to hit me."
Another reason the reader would think this is due to the fact that the man has been doing this regulary for the past 5 years. (stated in paragraph 1): "It’s exactly five years today that he’s been hitting me on the head with his umbrella. At first I couldn’t stand it; now I’m used to it."